Optical objective



July 22, 1941.

Ka /ME Search H00 [Mentor A.WARMI5HAN A ltorney U. Ul'llbb Patented July 22, 1941 Search H00 OPTICAL OBJECTIVE Arthur Warmisham, Leicesten England, assignor to Taylor, Taylor & Hobson Limited, Leicester, England, a company of Great Britain Application December 14, 1939, Serial No. 309,266

In Great Britain December 23, 1938 Claims.

This invention relates to optical objectives for photographic or projection or like purposes, corrected for spherical and chromatic aberrations and for coma, astigmatism, distortion and curvature of field, and comprising four axially aligned components separated by air gaps, the two inner components consisting of compound dispersive meniscus components, with their concave sur-' faces facing one another, whilst the two outer components consist of simple collective elements.

The invention has for its primary object to secure improved zonal spherical aberration correction or to reduce the higher order overcorrected spherical aberration in such an objective, and thereby to obtain in comparison with known objectives of this kind either a higher aperture with generally the same degree of correction or considerably improved correction at the usualv apertures.

In the objective according to the present invention one or each of the outer collective components is made of a glass having a mean refractive index higher than 1.75 and preferably higher than 1.8. Various examples of glass having such high refractive index are given in British Patent Specification No. 462,304, such glass having as its main constituents oxides of elements such as tungsten, tantalum, lanthalum, thorium, yttrium, zirconium, hafnium and colombium.

The sum of the numerical values of the curvatures of the front surface of the front dispersive component and the rear surface of the rear dispersive component conveniently lies between 4.25 and 4.85 times the reciprocal of the equivalent focal length of the objective.

When the relative aperture is not less than F/1.5, the sum of the numerical values of the nated by R1 R2 curvatures of the front and rear surfaces of the It is to be understood that the term "front as herein used refers to the side of the objective nearer to the longer conjugate and the term rear to that nearer the shorter conjugate.

Four convenient practical examples of objective according to the invention are illustrated respectively in the four figures of the accompanying drawing and numerical data therefor are given in the following tables, in which the radii of curvature of the individual surfaces are desigcounting from the front, the positive sign indicating that the surface is,

convex towards the front and the negative sign that it is concave thereto, whilst the thicknesses of the individual elements along the axis are designated by D1 D2 and the axial. air spaces between the various components by S1 S2 S3. The tables also give the mean refractive indices and the Abb V'numbers of the glasses used for the individual. elements.

Example I Equivalent focal length 1.000 Relative aperture F/2 Thickness or Refractive Abbe V Radms separation index no number D|=. 084 1 1.6130 59. 3 Rz= +5. 336

Dz=. 1332 1. 6130 59. 3 R4= 8628 Da=. 0594 1.6130 37. 4 R 2784 Sz=. 2244 Re= 3243 D 0 4=. 820 1. 6446 33. R1=+. 3955 5 D5=.1127 1. 6441 48. 3 Rs= 4394 'S:=. 0061 R9=+L 934 D6: 1332 1.8040 42. 4 Rl0= I. 168

Example II Equivalent local length 1.000 Relative aperture Fl 1. 5

Thickness or Refractive Abbe V Radius separation index my number Dl=- 0943 1. 804 42. 4 Rz=+3. 418

Dz=. 1332 1. 613 50. 3 R4= -5.'102

Sz=. 2246 o= 3464 S;=. 0062 Re= +1. 935

Do=. 1332 1. 804 42. 4 R -1. 186

Example III Equivalent focal length 1.000 Relative aperture F/l. 4

Thickness or Refractive Abbe V Radlus separation index no number Di=. 0862 1. 613 50. 4 R2=+7. 008

S 0021 Ri= 4204 Dz=. 1524 l. 613 59. 4 R4= +1. 752

Ds=. 0368 l. 621 36.1 R 2920 Sz=. 2102 R 3581 Da=. 1682 1. 644 48. 3 Ra= 5053 S 0021 Re= +3. 003

Dq=. 1209 1.850 42.0 R|o= -1. 067

Example IV Equivalent focal length 1.000 Relative aperture F/2 Thickness or Refractive Abb V Radms separation index on number Di=. 1066 1. 850 42. Rz= 3. 083

Da=- 0572 l. 613 37. 4 Ra=+. 2681 Sz=. 21 60 Re= 3122 D4=. 0789 l. 644 33. 5 R1= 6348 I Dr=. 1085 ,1. 644 48. 3 Ra= 4234 Ss=. 0059 R 1. 644

D.=. 0539 1.613 59. a Rio= 8468 It will be noticed that the high index glass is Example II 1.395, in Example Example IV 1.789.

All four examples show good zonal spherical aberration correction, the first two being almost perfectly corrected in this respect. Thus the maximum departure from paraxial fOClls in Example I is only .08%, and in Example II .14%, whilst in Example III, although greater than in III 1.335, and in Examples I and II, it is still only .50% and in Example IV it is 40%. All the examples also maintain the good correction for the other aberrations which is characteristic of well-designed objectives of the kind to which the invention.

relates.

What I claim as my invention and desire to secure by Letters Patent is:

1. An optical objective corrected for spherical and chromatic aberrations, coma, astigmatism, distortion and curvature of field, comprising four axially aligned lens components separated by air gaps, of which the itWO outer components consist of simple collective elements at least one of which is made of a glass having a. mean refractive index higher than 1.75, and the two inner components consist of compound dispersive meniscus components with their concave surfaces facing one another whilst the sum of the numerical values of the curvatures of their convex surfaces lies between 4.25 and 4.85 times the reciprocal of the equivalent focal length of the objective.

2. An optical objective corrected for spherical,

and chromatic aberrations, coma, astigmatism, distortion and curvature of field, having a relative aperture not less than F715 and comprising four axially aligned lens components separated by air gaps, of which the two inner component consist of compound dispersive meniscus components with their concave surfaces facing one another whilst the sum of the numerical values of the curvatures of their convex surfaces lies between 4.25 and 4.85 times the reciprocal of the equivalent focal length of the objective, and the two outer components consist of simple collective elements at least one of which is made of a glass having a mean refractive index higher than 1.8, the sum of the numerical values of the curvatures of the front and rear surfaces of the rear component being lent focal length of the objective.

3. An optical objective having numerical data as set forth in the following table;

employed in Examples I and. III for the rear component alone, in Example IV for the front component alone, and in Example II for both 1 front and rear components. The sum of the Example I Equivalent focal length 1.000. Relative aperture F/2 Thickness or Refractive Abbe V Radlus separation index m) number Dz=. 1332 1. 6130 .59. 3 R4= se2s Da=. 0594 I. 6130 37. 4 R5= 2784 Sz=. 2244 R 3243 V D5=. 1127 1. 6441 v 48. 3 R5 4394 v Sa=- 0061 3 Ra= +1. 934

55- UI'HUD 4. An optical objective having numerical data.

as set forth in the following table:

5. An optical objective having numerical delta.

as set forth'in the following table:

Search R00 Example II Example III 5 Equivalent focal length 1.000 Relative aperture F/l. 5 Equivalent focal length 1.000 Relative aperture F/1.4

Thickness or Refractive Abbe V Thickness or Refractive Abbe V Radms separation index 119 number Radms separation index 111) number R.=+. me 10 R1=+. 8369 D1==. 0043 1. 804 42. 4 D1=. 0862 1.613 59. 4 Rz=+3. 418 R:=-|-7. 008

S1=. 0359 &=. 0021 R3=+. 4474 Rs=+. 4204 Dz=. 1332 1. 613 59. 3 D:=. 1524 1. 613 59. 4 R4=-5. 102 R4=+1. 752

Da=. 0594 1. 613 31. 4 15 D3=. 0368 1. 621 as. 1 Rs=+. 2930 I R 2920 Sz=. 2246 Sz=. 2102 Ro=. 3464 Re=.3581

D4=. 0820 1. 6446 33. 5 D4=.0368 1. 6457 33. 9 R1=+. 4611 R1= 750s Ds=. 1128 1. 6441 48. 3 D5=. 1682 1. 644 48. 3 Ra=.4588 Ra=.5053

Sa=.0062 2O S3=.0021 Ro= +1. 935 Rn=+3. 003

Du=. 1332 1. 804 42. 4 Da= 1209 1. 850 42. 0 Rm==1.l86 RIF-L 067 

